Väljalaskesüsteemi projekteerimine üksikkorras valmistatud sõidukile

Käesoleva töö ülesanne oli projekteerida üksikkorras valmistatud sõidukile väljalaskesüsteem, mis vastaks nõutud tingimustele. Põhilised kriteeriumid, mida pidi järgima olid: vaba ruum( väga piiratud), mootori töö efektiivsuse tõstmine valitud tööpiirkondades, müratase ning mürgiste gaaside vähendamine. Eesmärkide saavutamiseks oli vaja tutvuda erinevate võimalustega, milliseid erinevaid süsteeme kasutatakse tänavasõiduautodel, milliseid võidusõiduautodel ning kuidas väljalaskesüsteemid üldse töötavad. Kuidas on võimalik tõsta mootori efektiivsust ning millised parameetrid seda oluliselt mõjutavad. Esiteks tuli teha kõige optimaalsem valik, milliseid konfiguratsioone kasutada kollektori valmistamisel. Kollektori ühendusflantsid väljalaskekanaliga valiti igale primaarkanalile inviduaalne flants, ennetamaks ühe pika flantsi termilist deformeerumist. Kollektori jagunemise skeemina kasutati 6-2-1konfiguratsiooni, sest eesmärgiks oli tõsta mootori efektiivsust madalamatel ja keskmistel pööretel. Järgmine etapp oli simuleerida virtuaalset mootori mudelit ning sinna projekteerida erinevad väljalaskesüsteemid ja analüüsida nende erinevusi. Põhimõte oli kontrollida arvutustulemusi, kas saadud väärtused rahuldavad soovitud tulemust või mitte. Viimaseks ning ka tähtsamaks etapiks võiks lugeda reaalset testimist veojõustendis. Testid teostati Tallinna Tehnikakõrgkooli veojõustendis Superflow Autodyn 883 AWD[13]. Selle eesmärk oli kontrollida teooriat, süsteemi projekteerimisel kasutatud valikuid ja virtuaalse simulatsiooni tulemusi. Veojõustendi tulemusgraafikutelt on näha, et soovitud tulemus on saavutatud. Kui soovitakse mõnele sõidukile efektiivseimat väljalaskesüsteemi, siis saavutatakse see ikkagi ainult testimise käigus. Teoorias on põhitõed välja toodud, kuid igale mootoritüübile võivad need erinevalt mõjuda. Samuti tuleb väga suurt rõhku panna pisidetailidele. Kindlasti peab alguses olema ka kindel visioon, mis eesmärgil mootorit või sõidukit kasutatakse.

Final thesis subject is „ Exhaust System Design for a Custom Car“. In the course of the thesis an exhaust system was designed for the custom car and the engine’s performance was optimised. As the vehicle will be used both on the street and on the track, the optimum choice is to better the engine’s capacity at low and medium revolutions. It is also important, that the engine’s power and moment do not fall to lower values than those for systems made in the factory. The main criteria, which had to be followed, were: free space (very limited), raising the efficiency of the engine, the level of noise and the content of toxic substances in exhaust fumes. In order to achieve the aims set, information has to be gathered, theories studied and different possible solutions had to be analysed. As the goal was to optimise the engine’s performance at medium and low revolutions, the collector configuration was chosen as 6-2-1. The BMW R-6 M50B25 engine is used for the vehicle. Dimensions for all channels are calculated according to the formula set out in the handbook. Generally the channel’s dimensions affect the external characteristics as follows: the diameter of the runner sets the moment’s peak value’s location at the desired engine revolutions, the length of the runner is used to affect the values of the moment near the peak value. A resonator is used as a muffling element in the system. The element consists of an internal pipe perforated directly through; it is surrounded by a rock wool and stainless steel case. The muffling capacity of the resonator is set by the physical size. The particular element is more effective at muffling high frequency sound. In order to reduce elements harmful to the environment contained in exhaust fumes, a catalytic converter is used, which has a spiral profile and a metal honeycomb. In comparison to a ceramic honeycomb it is more durable and thanks to larger openings it creates less backpressure in the system. Low backpressure is important for increasing the efficiency of the engine. In order to check the calculations and to analyse the effect of the catalytic converter, a virtual model of the engine was created using the Lotus Engine Simulation software. The purpose of the simulation was to analyse the differences of the engineered and original exhaust system. The comparison of the simulations showed the attainment of the aims. As the last phase both systems had to be tested in reality on a chassis dynamometer. The tests were carried out in the same conditions with different systems. The real result confirmed the results of the simulation, which is the increase of the moment and power at medium and high revolutions. The increase of the engine’s efficiency at higher revolutions is due to a shorter system and lower backpressure. On average the power increased by 2,3% and the moment by 1,6%. The price of the whole system came to about 2500 euros. The amount includes material expenses and time spent working. The price per hour of simple labour is set at 5 euros, on which 40 hours were spent and the price per hour of engineering is set at 10 euros, on which 160 hours were spent. It can be deduced from the results of the economic analysis that the given task is very expensive. The goals set have been achieved but due to the lack of opportunity the levels of exhaust fumes and noise have not been tested.